Process for producing alpha coating of chromium on objects of iron and steel or aluminum and particularly on knives, forks, and spoons



Patented May 17, 1932 UNITED STATES PA TEN-T Torrlee HEINIBJCH LEISER, or BERLIN-ERIEDENAI'I, GERMANY PROCESS FOR PRODUCING A COATING 0F CHROMIIIM ON OBJECTS OF IRON AND STEEL I OR ALUMINUM AND PARTICULARLY 0N KNIVES, FORKS, AND SPOONS v No Drawing. Application filed July 16, 1928, Serial No. 293,314, and in Germany July 21, 1 927.

A process for producing a coating of chromium on objects of iron and steel or aluminum and particularly on knives, forks and spoons.

For obtaining a shiny coating of chromium it was necessary until now to subject the ob jects in question to be coated electrically namely galvanically with chromium to an expensive mechanical pretreatment by grinding and polishing.

Such a pretreatment is commerciall possible for high grade metals, which are ree of pores and are smooth like brass, German silver and the like. However in the case of iron this pretreatment is so diflicult' and expensive that the costs are prohibitive, so that it is preferable to use instead of iron more expenlsiilie metals like brass, German silver and the Further it must be considered that the iron during the mechanical treatment is subject, to fine pores or surface cracks which must be removed with a corres onding considerable Waste of material, grin ing means and work.

I For instance in manufacturing spoons even if a ground and polished slieet'metal has been used the spoons after the rolling and press ing, etc., show pores and cracks or fissures so that it is necessary to again grind and polish which operation is very expensive;

. However just from such pores, cracks and fissures corrosion starts.

It is the purpose of the present invention to propose a method for obtaining shiny chromium coatings of a highly polished appearance on iron and steel in a cheap and reliable manner.

Corresponding to this method the objects after the operations of forming or before one of the last operations of forming in a manner known per se are coated with one or more intermediate layers of other metals before depositing the coating of chromium.

The invention in first line is distinguished by the feature that the inner coating layer for the objects,-which need not be polishedbefore, is applied in molten state, whereupon after applying the further intermediate metal layer the objects if desired without any further polishing step are provided With the chromium deposit galvanically, which deposit shows at once a shiny surface. The coating applied by melting in distinction from a galvanic coating fills out all.

pores and fissures, has a uite better adhesion or adherence and is thic er.

With particular'advantage tin is used for the innermost coating layer upon the iron.

By a last pressing or other smoothing operation before or after applying the second 6 intermediate layer consisting of brass the surface is improved and if necessary or desirable a further improvement can be obtained by treating the objects in a rotating drum by the sheradizing process. The relatively thick and tenacious coating of tin applied by melting is particularly well adapted for being smoothed by pressing.

The coatingv of brass can be applied galvanically. Preferably however also this sec- 0nd intermediate layer is heated at or after applying it. This second layer may be applied for example by spraying with the spraying gun or by, melting or by applying fine amorphous metal powders, which if necessary or desired can be alloyed byheating in a reducing atmosphere and are protected against oxidation in accordance with the nature of the metal.

After such treatment the chromium coating is deposited galvanically and has im mediately Claims a shiny surface.

1. A method for. covering with chromium objects formed from coarse-grained metals, as

comprising the steps of covering the objects with a coating of melted tin, arranging a second coating of an electro-positive metal thereon, and thereafter applying a coating of chromium thereon.

2. A method for covering with chromium forks and spoons or the like formed from iron, comprising the steps of melting on the objects a coating of tin, arranging a coating of'brass thereon, and chromium-plating the articles so formed.

3. A method for chromium-plating objects made from coarse-grain metals, withthe use of a plurality of intermediate metal' layers between the chromium and the base, comprlsing the steps of covering the objects with a coating of melted tin, arranging a second coating of an electro-positive metal thereon, and thereafter applying a coating of chromium thereon.

In testimony whereof I afiix m signature.

DR. HEINRICH EISER. 

